PhD: Cranial functional morphology during the origin of the archosaur body plan

Birds, dinosaurs, crocodilians, and pterosaurs all belong to the clade Archosauria, an extraordinarily diverse group that dominated terrestrial tetrapod faunas worldwide for nearly the entire Mesozoic Era, and is still highly successful today, with birds comprising around a third of extant tetrapod biodiversity. The diversification of archosaurs during the Triassic following the end-Permian mass extinction event fundamentally reshaped ecosystems on land.

Archosauria is part of a broader group, Archosauromorpha, which also includes a range of Permian and Triassic species more closely related to archosaurs than to lizards and snakes (lepidosaurs). These non-archosaurian archosauromorphs formed a significant component of Triassic ecosystems (>90 species) and were morphologically highly diverse, including highly specialised herbivores, large apex predators, marine predators with extremely elongated necks, and armoured crocodile-like forms.

The evolutionary success of archosaurs was underpinned by a distinctive body plan. Classic cranial anatomical features of archosaurs, including the antorbital and external mandibular fenestrae, the closed lower temporal bar, and serrated teeth, evolved in a mosaic fashion among archosauromorphs closely related to archosaurs. In addition, a number of early archosauromorphs evolved bizarre cranial adaptations, such as the extreme downturned premaxilla of proterosuchids.

Understanding the evolution of non-archosaurian archosauromorphs is critical to unravelling the origins of archosaurs during the Triassic, and taxonomic and phylogenetic work coupled with new discoveries have led to significant recent advances. However, rigorous functional morphological studies have not yet been conducted. This PhD project will characterise changes in cranial functional morphology through the evolutionary transition from basal archosauromorph to early archosaur. The functional significance of cranial modifications such as the acquisition of the antorbital fenestra will be tested, as well as the function of the proterosuchid premaxilla and other bizarre cranial adaptations.